chinesekiwi
Headphoneus Supremus
- Joined
- Feb 29, 2008
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I think digger945 was testing your sarcasm radar. It failed.
I think digger945 was testing your sarcasm radar. It failed.
I think digger945 was testing your sarcasm radar. It failed.
Every single part of the system is the same right down to the song. The only change is the USB to SPDIF converter. This past June makes one year comparing.
That's still not very specific. Are we talking hypothetically here or actual examples of what people are experiencing?
Whatever the case, my explanation would simply be that for some reason the amp outputs one of them at a higher volume than the other one. This can make people feel that the "bass is fuller" and basically feel like everything sounds better.
Originally Posted by 00940
-1- Waveform distortion: due to its physical properties, the cable can possibly affect the square waves, in interaction with the source and receiver (from that point of view they form an analog system). This in turns affect the accuracy of the recovered system clock fed to the DAC chip. This in turns affects the accuracy of the digital to analog conversion.
-2- Interaction in between power supply lines and data lines: it has been measured that 1Khz spikes coming from the data lines can couple into the power supply lines and that the longer the cable, the stronger the effect. Such spikes could maybe be directly heard as noise depending on the dac's pcb layout. Such spikes could also affect the accuracy of the ICs inside the dac, resulting either in increased jitter (for the clock or the receiver chip) or directly in higher distortion (for the dac chip and the opamps of the analog section).
-3- Rfi shielding: the usb cables are quite susceptible to high frequency noise pick-up (a reason among others why long runs cannot be used). Noise making its way into data line can perturbate the receiver chip, causing early/late triggers, resulting once again in a poorer system clock. If the noise couples into the power supply lines, see -2-.
-4- HF noise attenuation: the source computer signal's quality can vary widely. HF noise can find its way on the various USB lines. A cable attenuating this HF noise could thus have an impact. It could however interacts with -1-.
All these are sound engineering reasons and have been measured or could be, given time and the proper (read expensive) equipment. The fact that USB cables affect the analog output of the DAC seems to have been proven by measurements by Paul Miller for the january issue of Hifi News (if anyone has the article, I'd love to read more than hearsay).
HOWEVER, the existence of a technical difference in between cables does NOT prove the existence of an audible difference. It is even more so as the differences outlined above are fairly small and that cables manufacturers don't seem to bother measuring the actual differences their cables make. And you have to keep in mind before any generalization that USB audio uses 3 different protocols with various levels of weakness to those problems, that the USB receiver chips are very different and that DACs are coming from a bazillion different manufacturers who pay more or less attention to their designs.
I will not insist that a USB cable cannot possible impact the analog signal ...
... but it will be practically impossible to measure the change
DaBomb, can I solicit your views on audibility vs measurability? Would you, for example, state that because a thing cannot be measured therefore it cannot be audible? What about the other way around. Would you state that anything that is audible can de facto be measured? For example, I think we all would agree that some systems can project a much-prized "holographic soundstage". I know of no way of measuring that property. And I don't mean that we can't measure things that tend to correlate well with sound imaging. Just that we can't actually measure a system's imaging in any quantitative way. I am wondering, DaBomb, would you agree with that?
Originally Posted by ac500 /img/forum/go_quote.gif
giving the "believers" the benefit of the doubt, I ask: Do you still assert that USB cables can give you a different sound signature? Like boosting bass, for example?
Ok, so it's mostly just a debate regarding jitter.
In this case, I wonder if anyone with a buffered DAC would comment. A DAC running off a buffered data source and an internal clock should have no USB-dependent jitter whatsoever.